1. Field of the Invention
The present invention relates to an apparatus and a method for manufacturing a semiconductor device, and more specifically to a semiconductor device manufacturing apparatus and method for forming a titanium film or a titanium nitride film by use of a chemical vapor deposition process using a titanium halide as a raw material gas.
2. Description of Related Art
Now, a prior art semiconductor device manufacturing method for forming a titanium film and a titanium nitride film in a contact hole of a semiconductor device, by use of a chemical vapor deposition process using a titanium halide as a raw material gas, will be described with reference to FIG. 4, which is a diagrammatic view of a reaction chamber of a chemical vapor deposition apparatus for depositing a titanium film and a titanium nitride film by using a titanium halide as a raw material.
In a reaction chamber 300, a substrate holder 10 for holding a semiconductor substrate thereon, is formed of a nickel-based alloy having an excellent corrosion resistant property against chlorine. The substrate holder 10 is coated with a titanium nitride film (called a “pre-coated titanium nitride film” hereinafter) 13 in order to prevent the metal of the substrate holder 10 from reacting with a silicon of a bottom surface of a semiconductor substrate such a silicon substrate 1.
Here, the pre-coated titanium nitride film 13 is formed by a chemical vapor deposition process (called a “CVD process” hereinafter) performed in the reaction chamber 300 using titanium tetrachloride, ammonia and nitrogen as a raw material gas, before the process for depositing a film on the silicon substrate 1 is carried out.
A resistor heater 14 is incorporated in the substrate holder 10 to control the temperature of the substrate holder 10 in a film deposition process. An evacuating line 15 is provided for exhausting from the reaction chamber 300, a reaction gas generated in the course the film deposition process and an unreacted gas. An upper electrode 16 is provided at an upper portion of the reaction chamber 300.
Next, the prior art semiconductor device manufacturing method will be described with reference to FIGS. 5A to 5D, which are diagrammatic sectional views for illustrating various steps in the semiconductor device manufacturing process.
As shown in FIG. 5A, a device isolation oxide film 2 having a thickness of 200 nm is formed on a principal surface of a silicon substrate 1 by a conventional method, and a predetermined impurity is doped into the principal surface of the silicon substrate 1, so that a diffused layer 3 is formed.
Furthermore, an insulating film 4 having a thickness of 1500 nm is formed on the principal surface of the silicon substrate 1, and a portion of the insulating film 4 positioned on the diffused layer 3 is selectively removed so that a contact hole 5 is formed through the insulating film 4.
Thereafter, as shown in FIG. 5B, a titanium film 6 having a thickness of 10 nm is deposited on an upper surface of the insulating film 4 and an inner surface of the contact hole 5, by the CVD process using titanium tetrachloride, hydrogen and argon as a raw material gas. In the same process, a titanium silicide film 7 having a thickness of 20 nm is formed on the upper surface of the diffused layer 3.
Then, as shown in FIG. 5C, the titanium film 6 on the surface of the insulating film 4 is nitrided by ammonia in the reaction chamber 300 (FIG. 4), so that a titanium nitride film 8 is formed.
Furthermore, as shown in FIG. 5D, a titanium nitride film 9 having a thickness of 500 nm is deposited on a surface of the titanium nitride film and the titanium silicide film 7, by the CVD process using titanium tetrachloride, ammonia and nitrogen as a raw material gas.
In the above mentioned process for forming the titanium film and the titanium nitride film by using the titanium tetrachloride, since the substrate holder is exposed to an active chlorine atmosphere at a temperature of 500° C. to 600° C., the substrate holder is required to have the nature that a thermal deformation such as a thermal expansion and a plastic deformation is low, a high electric conductivity, a high heat conductivity and a high-temperature corrosion resistant property.
The vapor pressure of nickel chloride is the least within chlorides of refractory metals, and a nickel-based alloy is widely known as a heat resistant material for a structural member. In addition, the nickel-based alloy has some degree of electric conductivity and some degree of heat conductivity. Therefore, the nickel-based alloy has been used as a material of the prior art substrate holder. In addition, when a metal substrate holder is used, the pre-coated titanium nitride film is formed as mentioned above in order to prevent a reaction with the silicon of the bottom surface of the substrate.
If the substrate holder is formed of a ceramic material, since the ceramic material is low in heat conductivity, a long time is required to heat the substrate, and since the electric conductivity is low, the substrate potential varies in a high frequency discharge. These are problems.
A method for coating the metal substrate-holder with an insulating film by use of the CVD process is disclosed in Japanese Patent Application Pre-examination Publication No. JP-A-03-183151, (the content of which is incorporated by reference in its entirety into this application, and also an English abstract of JP-A-03-183151 is available from the Japanese Patent Office and the content of the English abstract of JP-A-03-183151 is also incorporated by reference in its entirety into this application). In the method disclosed in JP-A-03-183151, the coating of the metal substrate-holder upper surface by the insulating film is previously carried out in a predetermined reaction chamber which is different from the reaction chamber in which the metal substrate-holder is to be installed. Therefore, the insulating film formed in the predetermined reaction chamber is required to resist to a heat stress caused by a heat history from an ordinary room temperature to a process temperature. Accordingly, the combination of the metal material used to form the substrate holder with the insulating film formed on the upper surface of the metal substrate-holder is restricted to ones which have a thermal characteristics near to each other.
However, the following problem has been encountered in the prior art semiconductor device manufacturing apparatus and method mentioned above.
Since the substrate holder is coated with the precoated titanium nitride film, it is possible to prevent the reaction between the silicon of the substrate bottom surface and the metal of the substrate holder. However, the nickel and the other metal(s) of the substrate holder are corroded through the precoated titanium nitride film by active chlorine generated in the process of depositing the titanium film and the titanium nitride film by using the titanium tetrachloride.
As the result of the corrosion, a vapor of nickel chloride and chloride of the other metal(s) is generated in the reaction chamber, with the result that nickel and the other metal(s) are deposited on the surface of the silicon substrate because of a silicon reduction reaction of the chloride of the nickel and the other metal(s) at the surface of the silicon substrate. The nickel and the other metal(s) deposited on the substrate surface diffuse into the interior of the substrate when the substrate holder temperature is high. As a result, impurity energy level(s) caused by the contaminating metals are formed in a junction near to the contact hole in the semiconductor device, so that a junction leakage current is apt to occur, and therefore, a stable electric characteristics of the contact electrode cannot be obtained.